I would like to create an external battery for my laptop. The charger for my laptop says 19.5V 7.7A. I asked chat GPT to design a battery pack for me and it gave me the response shown below my questions.

My questions are:

1. Is it ok to input 24v into my laptop despite it saying 19.5 volts?

2. I was considering making a 6S6P battery pack but it looks cheaper to buy one pre assembled. Is there anything to gain by building my own such as battery quality?

From ChatGPT:

To create a power supply of 19.5 volts at 7.7 amps for 2 hours using 18650 batteries, you need to consider both the voltage and capacity requirements. 18650 batteries typically have a nominal voltage of about 3.7 volts and capacities that can vary, usually between 1800mAh to 3500mAh. For the sake of this example, let's assume we use 18650 batteries with a capacity of 3000mAh (or 3Ah).

Voltage Requirement (Series Configuration): - To achieve 19.5 volts, you need to connect several batteries in series. Each battery adds 3.7 volts, so divide the target voltage by the voltage of one battery: 19.5V ÷ 3.7V ≈ 5.27. Since you can't have a fraction of a battery, you'll need to round up to the nearest whole number, which is 6 batteries in series. This will give you 22.2V (6 x 3.7V), slightly above your target but typically acceptable for most 19.5V applications.

Capacity Requirement (Parallel Configuration): - Next, to meet the amp-hour requirement, you need to calculate the total capacity needed: 7.7 amps for 2 hours equals 15.4Ah (7.7A x 2h). Each 18650 battery has 3Ah, so divide the total required capacity by the capacity of one battery: 15.4Ah ÷ 3Ah ≈ 5.13. Round this up to the nearest whole number for practical purposes, which is 6.

Combining Series and Parallel: - You need 6 batteries in series to achieve the necessary voltage and 6 parallel sets of these series strings to meet the capacity requirements. Therefore, you will need 6 batteries in series multiplied by 6 in parallel, totaling 36 batteries (6S6P).

Final Configuration: - Your battery pack will consist of 6 sets of 6 batteries each. Each set of 6 is connected in series (to achieve the required voltage), and these 6 sets are then connected in parallel (to achieve the required capacity and duration).

This setup will give you a battery pack that exceeds the required voltage slightly and meets the capacity requirement to provide 7.7 amps for 2 hours. However, it's important to consider that actual performance can vary due to factors like battery efficiency, discharge rates, and real-world conditions. Also, proper battery management and safety measures are crucial, especially when dealing with lithium-ion batteries.